1、托福-5 (1)及答案解析(总分：148.50，做题时间：90 分钟)一、READING(总题数：0，分数：0.00)二、Part 1(总题数：1，分数：6.50)Natural SelectionFirst coined by Darwin, the term natural selection refers to the process at the core of evolutionary theory. Simply put, Darwin believed that every living organism had to struggle to survive and reprod
2、uce. By random chance, some individuals in a species would have characteristics that made them better adapted to this struggle than their contemporaries. Such individuals would be more likely to reproduce and pass their characteristics on to their offspring. Over many generations, a series of small
3、differences in characteristics would accumulate, until eventually the creatures that were produced would be so different from their original ancestors that they would constitute a new species. (A) Although Darwin did not know how variations between individual members of the same species were able to
4、 arise in the first place or how such traits could then be passed on from species to species, we now know that this process occurs through genes. (B) Genes determine what characteristics an organism will possess, from its size to its skin color to its gender. (C) Sometimes these genes become damaged
5、 or altered-a process known as mutation. (D) Most mutations are either too small to have any effect, or have detrimental effects on the organism. A few, however, can be beneficial to helping an organism survive. The organisms with these beneficial mutations are the ones that .survive and reproduce,
6、passing their particular genetic mutation on to future generations.Originally, Darwin thought that two particular types of traits were naturally selected for evolution. The first type included any and all traits that helped an organism survive, either by giving it easier access to food, better prote
7、ction from predators, or superior adaptability to shifting environmental conditions. Several examples of the natural selection of such traits have been observed since Darwin first proposed his theory. The most often cited example is the coloration of moths near industrial centers. Some of them have
8、white wings and the others have black wings. Under normal conditions, the lighter-colored moths predominate since white moths are less visible against the light-colored bark of the trees in the forests where they live, which means they can more easily avoid predators. Near industrial centers, howeve
9、r, darker-colored moths predominate, as the pollution from the factory has darkened the bark of the nearby trees. Moths landing on these trees are much more difficult to see if they have black wings. This trait has now become most common in moth populations living in areas where pollutants have chan
10、ged the color of the tree bark.The second type of naturally selected traits envisioned by Darwin involved those characteristics of an organism that made it easier for that organism to find a mate. This form of natural selection, often called sexual selection, was thought to explain the existence of
11、highly developed traits in certain animals that seemed to play no particular role in their survival, and that in some cases seemed to make it even harder for them to survive. A prime example of such a trait is the peacocks elaborate, colorful tail feathers. A long, unwieldy tail that can expand into
12、 a display of bright colors that draws the attention of any predator in the vicinity seems less likely than that of other kinds of birds to help the bird survive. However, researchers discovered that peahens invariably chose to mate with those peacocks whose tail feathers produced the most artistic
13、displays. Thus, although the peacocks tail feathers have no adaptive function in terms of coping with survival pressure, the gene that controls feather color is the one that is most likely to be passed on because of its role in the mating process.Many scientists now believe that a third type of natu
14、rally selected characteristics exists, namely those that may be harmful to an individual organism but beneficial to that organisms species. This helps to explain the persistence of certain traits that were viewed under traditional evolutionary theory as not assisting in adaptation. For instance, in
15、many animal species, including humans, a small subset of the population is homosexual. Under the old view of evolution, this could not be accounted for since homosexual individuals do not normally reproduce, meaning the gene that codes for it should have long been phased out of the gene pool. Howeve
16、r, recent studies among wild sheep populations have found that the prevalence of homosexuality in the sheep population increases in times of severe food shortages, causing the sheep to form stronger bonds with sheep of the same sex than they otherwise would. As a result, instead of fighting over a p
17、articular food source, these sheep share the food they find with each other, increasing the species chance of surviving hard times. Though still controversial, the idea that traits may be naturally selected because of their benefits to the species instead of their benefits to the individual is rapid
18、ly gaining acceptance in the scientific community because of the wide array of characteristics that it can explain, including the human tendency towards altruism,（分数：6.50）(1).The word “them“ in the passage refers to（分数：0.50）A.characteristics.B.individuals.C.species.D.contemporaries.(2).According to
19、paragraph 1, what is the end result of natural selection?（分数：0.50）A.Special individuals.B.New species.C.Random traits.D.Adapted characteristics.(3).Look at the four squares in the passage that indicate where the following sentence can be added to the passage.All of the information about an organisms
20、 physiology is contained in its DNA, which is a strand of organic chemicals composed of sequences of nucleotides called genes.Where would this sentence best fit?（分数：0.50）A.()B.()C.()D.()(4).All of the following are listed as factors that might make a trait beneficial to an organism EXCEPT its abilit
21、y to help the organism（分数：0.50）A.resemble other individuals.B.avoid predators.C.find nourishment.D.survive chang(5).The word “particular“ in the passage is closest in meaning to（分数：0.50）A.exacting.B.noteworthy.C.precise.D.specifi(6).According to paragraph 2, why was dark coloration selected for moth
22、s living near industrial areas?（分数：0.50）A.It camouflaged them from enemies.B.It made them easier to see than lighter-colored moths.C.It helped male moths attract mates.B. It allowed them to find food more rapidly.(7).The word “involved“ in the passage is closest in meaning to（分数：0.50）A.engaged.B.req
23、uired.C.included.D.implie(8).Why does the author mention the peacocks tail feathers?（分数：0.50）A.To contrast the peacocks appearance with that of moths.B.To show that not all traits are naturally selected.C.To provide an example of a sexually selected trait.D.To demonstrate the power of environmental
24、pressures.(9).What do peahens look for in peacocks?（分数：0.50）A.Large wing feathers.B.Loud mating calls.C.Artistic tail displays.D.Colorful breast plumag(10).The word “prevalence“ in the passage is closest in meaning to（分数：0.50）A.dominance.B.occurrence.C.primacy.D.increas(11).Which of the following se
25、ntences best expresses the essential information in the highlighted sentence in the passage? Incorrect answer choices change the meaning of the sentence in important ways or leave out essential information.（分数：0.50）A.Scientists are finding the idea that some traits are naturally selected for their b
26、enefits to the species increasingly useful.B.It is widely accepted by the scientific community that individuals that dont benefit their species are maladaptive.C.The human tendency towards altruism is one widely accepted example of a trait traditionally associated with natural selection.D.The contro
27、versy over the idea that traits can be selected based on their benefits to species instead of individuals is inevitabl(12).What can be inferred from paragraph 4 about the third type of naturally selected characteristics?（分数：0.50）A.There is nothing controversial about the now widely accepted view tha
28、t some traits are selected because they benefit the species.B.The old view of evolution is utterly wrong and needs to be replaced with a wholly new theory of the creation of species.C.The gene for homosexuality will eventually be completely phased out of the gene pool for every living species.D.The
29、human trait of being altruistic is more beneficial to humankind as a whole than it is to any particular human bein(13).Directions: An introductory sentence to a brief summary of the passage is given below. Complete the summary by adding the THREE answer choices that express the most important ideas
30、in the passage. Some answer choices do not belong in the summary because they express ideas that are not given in the passage or are minor ideas in the passage. This question is worth 2 points.Natural selection is the name given by Darwin to the process whereby new species evolve over time as indivi
31、duals with useful traits survive and reproduce, passing those traits on to new generations._Answer Choices1. Darwin believed that natural selection favored organisms that had traits that could help them find food and survive predator attacks and environmental pressures.2. Darwin explained advanced t
32、raits that did not seem to affect an organisms survival as being characteristics useful in finding a mate.3. Moths near industrial centers evolve dark coloration when the trees in which they live are blackened by pollution from nearby factories.4. Recently, scientists have expanded the idea of natur
33、al selection to include traits that benefit the species as a group, even when those traits seem harmful to the particular individuals who possess them.5. The peacocks colorful tail feathers are meant to attract peahens, which view the bright colors involved in the display as a sign of the males good
34、 health.6. Religious groups opposition to evolutionism has led some schools to reconsider teaching it, even though it is an established scientific theory with much evidence to prove it.（分数：0.50）填空项 1:_三、Part 2(总题数：2，分数：13.00)Continental DriftContinental drift, and the subsequent theory of plate tect
35、onics, forms the modern framework for geological study of the Earth. Continental drift stems from scientific notions as early as the 16th century that the Earths continents were once a single land mass, which scientists have termed Pangaea, meaning “all lands“ in Greek. In 1912, German meteorologist
36、 Alfred Wegener proposed that natural forces such as earthquakes and floods broke Pangaea apart between 225 and 200 million years ago, and it eventually fragmented into the continents as we know them today. Wegener based his theory on four major observations: first, the amazing fit of the African an
37、d South American continents; second, the similarities of unusually structured plant and animal fossils discovered along the coastlines of South America and Africa, even though they are separated by the Atlantic Ocean; third, similarities in rocks and ice sheets on these two continents; and fourth, e
38、vidence that some ancient climates were diametrically opposite of modern ones.Wegeners theory of continental drift would eventually spark a new way of viewing the Earth. Initially, however, colleagues generally dismissed it as absurd, despite the fact that it seemed to complement available scientifi
39、c information. Their primary criticism was Wegeners inability to adequately explain how the large masses of land could drift such great distances. (A) Wegener speculated that they simply plowed through the ocean floor, but English geophysicist Harold Jeffreys refuted that contention, noting that it
40、is physically impossible for a gargantuan mass of solid rock to do so without breaking up. (B) It was not until the 1950s-two decades after Wegeners death-that technological advances enabled scientists to confirm Wegeners hypotheses. Improved techniques in ocean floor mapping revealed that the botto
41、m of the ocean was not mostly flat and featureless as most scientists had speculated, and that geologic processes on land, such as earthquakes and volcanic eruptions, were linked to dynamics on the ocean floor. (C) Scientists discovered that hot rock boils up from the Earths mantle1 near ridges in t
42、he middle of the ocean, spreading over the sea floor and forming new oceanic crust. (D) As this crust spreads, it moves continents an average of one or two centimeters each year. Scientists also found that as new crust forms at ocean ridges, older crust descends into trenches2 at the rim of the Paci
43、fic Ocean Basin, effectively recycling the ocean basins and maintaining the Earth at a steady size. Seismic activity is most prominent in earthquake zones parallel to these trenches at the edge of continents, likely due to the fact that sinking crust melts, causing hot rock to bubble up, leading to
44、eruptions and violent quaking.These findings on the ocean floor led to the theory of plate tectonics, which holds that the Earths outermost layer consists of more than a dozen large and small plates-massive slabs of solid rock, both above and beneath the water-that are drifting about the surface of
45、the Earth, occasionally colliding, rubbing against each other, clustering and separating, and even disappearing completely under one another. These interactions are constantly shaping the face of the planet, signified by the term “tectonics“ from the Greek word meaning “to build.“ The results of pla
46、te-tectonic forces are most evident at plate boundaries-narrow zones between plates. At divergent boundaries, plates pull away from each other, creating new crust. A prominent example can be seen in Iceland, which is splitting as the North American Plate moves westward relativeto the Eurasian Plate.
47、 At convergent boundaries, crust is destroyed as one plate dives under another. This tends to form mountain ranges on continental, or surface, plates, such as the South American Andes and the Asian Himalayas. At transform boundaries, plates slide horizontally past each other and crust is neither cre
48、ated nor destroyed. Since the plates lack smooth edges, pressure is generally built up and suddenly released, making these types of boundaries-such as the San Andreas Fault in California-particularly susceptible to earthquakes. At a fourth type of boundary, called plate boundary zones, there are bro
49、ad areas where boundaries are ill-defined and the effects of plate interaction are not well understood. Because plate boundary zones feature at least two large plates and one small plate caught between them, they have complicated geological structures and earthquake patterns. The theory of plate tectonics has gained widespread scientific acceptance, though there still remains debate over s
